The distribution of below ground biomass within monotypic stands of invasive Phragmites australis (Common Reed) was documented from a series of oligo-, meso-, and polyhaline coastal marshes in New Hampshire. Soil profiles were described, and live biomass was documented growing to a maximum depth of 95 cm for roots and 85 cm for rhizomes. Our data show that invasive P. australis utilizes a greater depth range than native graminoids (90% within the top 70 cm and top 20 cm, respectively). We corroborate prior anecdotal observations and provide further evidence illustrating the potential for this invasive plant to access resources (i.e., water and nutrients) at depths greater than the native species with which it competes.